Polls suggest the Scottish referendum battle remains too close to call as both sides gear up for a frantic last day of campaigning.
Surveys for The Daily Telegraph and ICM for The Scotsman both gave No a slender lead of 52% to 48%.
But the four-point advantage is close to the margin of error for such research - raising the prospect of a nailbiting final push in which every ballot could make the difference.
The leaders of the three main political parties in the UK have signed a pledge for more powers for Scotland if it rejects independence.
British Prime Minister and Conservative party leader David Cameron, Labour leader Ed Miliband and leader of the Liberal Democrats, Deputy Prime Minister Nick Clegg have signed the letter.
It appeared on the front page of the Daily Record newspaper.
The letter promises "extensive new powers" for the Scottish Parliament "delivered by the process and to the timetable agreed" by the three parties.
The Yes campaign said a vote for independence in Thursday's referendum is the only way to guarantee Scotland gets the powers it needs.
In the letter, the party leaders say they agree that "the UK exists to ensure opportunity and security for all by sharing our resources equitably across all four nations".
The joint letter also states: "And because of the continuation of the Barnett allocation for resources and the powers of the Scottish Parliament to raise revenue, we can state categorically that the final say on how much is spent on the NHS will be a matter for the Scottish Parliament."
First Minister Alex Salmond has dismissed the Westminster pledge as a "last-minute desperate offer of nothing".
The First Minister told BBC Radio Scotland's Good Morning Scotland: "This so-called vow that has been in the Daily Record, I suspect it's been called a vow because the last time one of these leaders made a pledge and signed the pledge was the Deputy Prime Minister Nick Clegg when he signed a pledge that he wouldn't have tuition fees and then promptly put them up to £9,000 for English students in England.
"It's a classic example of how this last-minute desperate offer of nothing is not going to dissuade people in Scotland from the huge opportunity of taking Scotland's future into Scotland's hands this coming Thursday."
Miliband criticises 'ugly' tactics
Elsewhere, Ed Miliband has accused the pro-independence campaign of "ugly" tactics after campaigners hurled abuse at him in chaotic scenes during a visit to Edinburgh.
The Labour leader was branded an "absolute liar" by protesters when he toured the St James Shopping Centre in what was supposed to be a trip to persuade undecided voters in the final stages of the referendum battle.
Shoppers were trampled and pushed aside as campaigners from both the Yes and the No camps clashed during the walkabout.
Mr Miliband struggled to speak to voters amid the frenzy and the visit was quickly brought to an end.
Among the few members of the public he was able to chat to, one was a visitor to the city and the other declared themselves a Yes supporter.
Mr Miliband told the BBC: "I think we have seen in parts of this campaign an ugly side to it from the Yes campaign.
"I think debates should be conducted in a civilised way. I think that's very, very important, but I understand that passions run high.
"What I've enjoyed about this campaign, including today when I get the chance, is meeting people who are genuinely undecided."
Thousands of people attended a last-minute rally in central London yesterday where celebrity campaigner Bob Geldof urged voters in Scotland to remain part of the United Kingdom.
Speaking to the crowd, Mr Geldof said that all of the UK was disillusioned with parliament and that Scotland needed to stay to help resolve the issue.
"I'm Irish ... I couldn't make a go of it there. I came to this amazing country.
"I owe my life. I have that immigrant's gratitude to this country. Being here is part of the payback."
The musician and activist said that the United Kingdom was "one of the greatest ideas ever invented for the modern age".
He said a Yes vote in this week's referendum would be a regression to a mythical, 18th Century notion.
"There is such a thing as a great big glorious 'no'. No is not always a negative," he told the crowd.
